As a protection-purpose circuit breaker for performing a current switching operation in an electric power system, a gas circuit breaker in which an electric current is cut off by filling an arc extinguishing gas into a hermetically-sealed container formed of a grounded metal or a porcelain bushing is widely used.
As one example of conventional gas circuit breakers, a double-point-break gas circuit breaker having two interrupting chambers is shown in FIG. 11.
FIG. 11 is a frontal sectional view of a conventional gas circuit breaker.
The conventional gas circuit breaker includes a container 101, a support insulation tube 103, interrupting chambers 104, a breaker unit 105, a fixed contact 106, a movable contact 107, a first link group 108, an insulating operation rod 109, a unit box 110, an operating mechanism 111, an actuator 112, an output shaft 113, a second link group 114, container supports 115 and an base 116.
The container 101 is filled with an arc extinguishing gas such as SF6 (sulfur hexafluoride) or CO2 (carbon dioxide). The support insulation tube 103 is installed substantially perpendicularly to an axial direction of the container 101, at a nearly central position in the axial direction of the container 101. The breaker unit 105 provided with two interrupting chambers 104 (the right interrupting chamber omitted in FIG. 11) is supported by the support insulation tube 103.
Each of the interrupting chambers 104 includes a fixed contact 106 fixed in a specified position of the container 101 and a movable contact 107 movable in the axial direction of the container 101. The fixed contact 106 and the movable contact 107 are arranged to face each other.
The insulating operation rod 109 extending through a substantially central portion of the support insulation tube 103 is connected through the first link group 108 to an end of the movable contact 107 opposite to the fixed contact 106.
Attached to the external portion of the container 101 is the unit box 110 in which the operating mechanism 111 is placed.
The operating mechanism 111 includes an actuator 112 and a hydraulic mechanism or a spring mechanism, which are not shown in the drawings. The actuator 112 converts the energy generated by the hydraulic mechanism or the spring mechanism (not shown) to a driving force required in a switching operation of electrical contacts.
One end of the insulating operation rod 109 and an output shaft 113 of the actuator 112 are connected to each other through the second link group 114, wherein the insulating operation rod 109 and the output shaft 113 of the actuator 112 are in a positional relationship of about 90 degrees.
The container 101 is installed on the base 116 by the container supports 115 arranged in, e.g., four corners.
In the conventional gas circuit breaker as configured above, the driving force of the actuator 112 acting in the direction of arrow G is transferred to the movable contact 107 via the second link group 114, the insulating operation rod 109 and the first link group 108, thereby driving the movable contact 107 in the direction of arrow G. In other words, the driving force of the actuator 112 acting in the direction of arrow G is first converted to a force in a direction of arrow H by the second link group 114 and is then converted to a force in the direction of arrow G by the first link group 108.
As the movable contact 107 is driven in the direction of arrow G, the fixed contact 106 and the movable contact 107 are contacted and separated from each other, consequently performing the switching operation of a circuit.
In the conventional gas circuit breaker stated above, due to the use of two link groups 108 and 114, the energy loss during the transfer of the driving force of the actuator 112 to the movable contact 107 becomes larger.